Judge rules against ex-Trump campaign boss

US President Donald Trump's former campaign manager Paul Manafort breached his plea agreement with Special Counsel Robert Mueller's office by intentionally lying to prosecutors, a federal judge has ruled.

The ruling concludes weeks of wrangling between Manafort's lawyers and the special counsel over whether he had intentionally lied to prosecutors, impeding their investigation into Russian interference in the 2016 US election.

Judge Amy Berman Jackson in the US District Court for the District of Columbia found a "preponderance" of evidence Manafort lied on three different topics, including his communications with former business partner Konstantin Kilimnik.

She cleared Manafort of allegations he intentionally lied on two other subjects.

As a result of the verdict, Special Counsel Mueller's office is no longer required to support a sentencing reduction for Manafort.

The ruling follows last week's release of a court transcript that showed Mueller's team believed Manafort's alleged lies were central to their investigation into potential collusion, which Trump and Russia have both denied.

The investigation appears focused on a meeting held at the height of the election campaign between Manafort and Kilimnik, whom prosecutors say has ties to Russian intelligence, according to the court filing.